A switch device is an essential device in a circuit, which functions to turn on or turn off the circuit. In a process of turning off a switch contact, the arc-extinguishing needs to be performed, such that the contact is enabled to be turned off resolutely and prevent the arc from raising the temperature of the switch and even damaging the switch. As the vacuum switch has small gaps, high voltage-resistant capability, low arc voltages, high current breaking capability, low electrical erosion, and long electrical endurance, the vacuum switch has been widely applied in power circuits.
A core member of a vacuum switch tube is a vacuum arc-extinguishing chamber in a shell. The performance of the contacts inside the vacuum arc-extinguishing chamber directly decides the performance of the vacuum switch tube. Rear ends of the vacuum switch tube are respectively connected to a dynamic conductive rod and a static conductive rod. A motion of turning off the contact is to disconnect the contact mechanically by operating the dynamic conductive rod. When the contact is being turned off, a contact area of the contact becomes increasingly small, till the contact has only one contact point. At the same time, a contact resistance is increased and a regional temperature is raised. Until the contact point is melted, evaporated, and ionized, the metal vapor maintains the discharging in vacuum, so as to generate a vacuum arc and eventually accomplish the electrical disconnect of the contact.
A defect in the prior art is that, the vacuum switch tube usually fails to form a desirable vertical magnetic field for performing arc-extinguishing due to the restriction of a structural shape, such that problems such as electric field concentration, insufficient voltage resistance, and high re-ignition possibility during the high voltage breaking process are difficult to be solved. For a high voltage circuit, only the 36-kilovolt voltage breaking can be realized. For a higher voltage circuit, particularly, 72-kilovolt high voltage circuit, currently, no vacuum switch tube structure is available for satisfying effective arc-extinguishing requirements during the breaking process.